Shared blockchain data storage

ABSTRACT

Disclosed herein are methods, systems, and apparatus, including computer programs encoded on computer storage media, for communicating and sharing blockchain data. One of the methods includes sending current state information associated with a current block of a blockchain to one or more shared storage nodes of the blockchain network; sending a hash value to the one of the one or more shared storage nodes for retrieving an account state stored in the historic state tree; receiving the account state in response to sending the hash value; and verifying, by the consensus node, that the account state is part of the blockchain based on the hash value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of priorityof U.S. patent application Ser. No. 16/928,794, filed Jul. 14, 2020,which is a continuation of U.S. patent application Ser. No. 16/714,197,filed Dec. 13, 2019, now U.S. Pat. No. 10,826,709, which is acontinuation of PCT Application No. PCT/CN2019/095625, filed on Jul. 11,2019, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This specification relates to shared storage of blockchain data.

BACKGROUND

Distributed ledger systems (DLSs), which can also be referred to asconsensus networks, and/or blockchain networks, enable participatingentities to securely, and immutably store data. DLSs are commonlyreferred to as blockchain networks without referencing any particularuser case. Examples of types of blockchain networks can include publicblockchain networks, private blockchain networks, and consortiumblockchain networks. A consortium blockchain network is provided for aselect group of entities, which control the consensus process, andincludes an access control layer.

Blockchain-based programs can be executed by distributed computingplatform such as an Ethereum. For example, the Ethereum virtual machine(EVM) provides the runtime environment for smart contracts in Ethereum.An Ethereum blockchain can be viewed as a transaction-based statemachine. State data in an Ethereum can be assembled to a globalshared-state referred to as a world state. The world state comprises amapping between Ethereum account addresses and account states. The worldstate can be stored in data structures such as the Merkle Patricia tree(MPT).

Besides state data, blockchain networks can also store other types ofdata such as block data and index data. Block data can include blockheader and block body. The block header can include identity informationof a particular block and the block body can include transactions thatare confirmed with the block. When more and more transactions areentered into the blockchain, state data and block data can grow verylarge in size. In some DLSs, every node stores an entire copy of theblockchain, which can take large amount of storage spaces, even if someof the old block data or state data are not frequently visited.

Accordingly, it would be desirable to reduce the amount of data storedon at least some of the nodes in the DLS to save storage cost withoutsignificantly affecting processing efficiency.

SUMMARY

This specification describes technologies for communicating and sharingblockchain data. These technologies generally involve sending, by aconsensus node of a blockchain network, current state informationassociated with a current block of a blockchain to one or more sharedstorage nodes of the blockchain network, wherein the consensus nodestores the current state information and the one or more shared storagenodes store historic state information associated with every block ofthe blockchain as a historic state tree, and wherein the historic statetree includes key-value pairs (KVPs) with values being account states ofaccounts associated with the blockchain network and keys being hashvalues of the corresponding account states; sending, by the consensusnode, a hash value to the one of the one or more shared storage nodesfor retrieving an account state stored in the historic state tree;receiving, by the consensus node, the account state in response tosending the hash value; and verifying, by the consensus node, that theaccount state is part of the blockchain based on the hash value.

This specification also provides one or more non-transitorycomputer-readable storage media coupled to one or more processors andhaving instructions stored thereon which, when executed by the one ormore processors, cause the one or more processors to perform operationsin accordance with embodiments of the methods provided herein.

This specification further provides a system for implementing themethods provided herein. The system includes one or more processors, anda computer-readable storage medium coupled to the one or more processorshaving instructions stored thereon which, when executed by the one ormore processors, cause the one or more processors to perform operationsin accordance with embodiments of the methods provided herein.

It is appreciated that methods in accordance with this specification mayinclude any combination of the aspects and features described herein.That is, methods in accordance with this specification are not limitedto the combinations of aspects and features specifically describedherein, but also include any combination of the aspects and featuresprovided.

The details of one or more embodiments of this specification are setforth in the accompanying drawings and the description below. Otherfeatures and advantages of this specification will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example of an environment that can be used to executeembodiments of this specification.

FIG. 2 depicts an example of an architecture in accordance withembodiments of this specification.

FIG. 3 depicts an example of a fixed depth Merkle tree (FDMT) datastructure in accordance with embodiments of this specification.

FIG. 4 depicts examples of databases for storing blockchain data inaccordance with embodiments of this specification.

FIG. 5 depicts an example of a blockchain network using shared storagein accordance with embodiments of this specification.

FIG. 6 depicts another example of a blockchain network using sharedstorage in accordance with embodiments of this specification.

FIG. 7 depicts yet another example of a blockchain network using sharedstorage in accordance with embodiments of this specification.

FIG. 8 depicts an example of a process that can be executed inaccordance with embodiments of this specification.

FIG. 9 depicts examples of modules of an apparatus in accordance withembodiments of this specification.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

This specification describes technologies for communicating and sharingblockchain data. These technologies generally involve sending, by aconsensus node of a blockchain network, current state informationassociated with a current block of a blockchain to one or more sharedstorage nodes of the blockchain network, wherein the consensus nodestores the current state information and the one or more shared storagenodes store historic state information associated with every block ofthe blockchain as a historic state tree, and wherein the historic statetree includes key-value pairs (KVPs) with values being account states ofaccounts associated with the blockchain network and keys being hashvalues of the corresponding account states; sending, by the consensusnode, a hash value to the one of the one or more shared storage nodesfor retrieving an account state stored in the historic state tree;receiving, by the consensus node, the account state in response tosending the hash value; and verifying, by the consensus node, that theaccount state is part of the blockchain based on the hash value.

The techniques described in this specification produce several technicaleffects. For example, embodiments of the subject matter can allowsavings of storage resources of blockchain nodes without significantlysacrificing computational efficiency. Because most data in the historicstate tree are “cold” data that are infrequently used, by saving the“cold” data only in the shared storage nodes, usage rate of storagespace across the blockchain network can be significantly improved. Ifthe share storage node is a POA node or elected by voting based on PBFTconsensus, the historic state tree only needs to be stored in the sharestorage node instead of storing on every blockchain node. If sharedstorage nodes are part of the blockchain consensus nodes without POA,for an N consensus nodes blockchain network, where N equals 3f+1, 3f+2,or 3f+3, where f is the number of maximum faulty consensus nodes,(N−f−1)/N of the blockchain consensus nodes only need to store “hot”data as a current state tree, instead of both “cold” and “hot” data asthe historic state tree.

Moreover, for the N consensus nodes blockchain network where f+1 nodesare used as shared storage nodes to store the historic state tree, amaximum off faulty consensus nodes can be tolerated. In other words, thesaving of storage space does not compromise data reliability. Theconsensus nodes of the blockchain network can be properly served bytolerating f faulty consensus nodes and saving the entire copy ofblockchain only on f+1 nodes. Because the reliability of the system isensured by the f+1 shared storage node, data security can be improvedand relatively independent from the security level of the underlyingservice platform.

To provide further context for embodiments of this specification, and asintroduced above, distributed ledger systems (DLSs), which can also bereferred to as consensus networks (e.g., made up of peer-to-peer nodes),and blockchain networks, enable participating entities to securely, andimmutably conduct transactions, and store data. Although the termblockchain is generally associated with particular networks, and/or usecases, blockchain is used herein to generally refer to a DLS withoutreference to any particular use case.

A blockchain is a data structure that stores transactions in a way thatthe transactions are immutable. Thus, transactions recorded on ablockchain are reliable and trustworthy. A blockchain includes one ormore blocks. Each block in the chain is linked to a previous blockimmediately before it in the chain by including a cryptographic hash ofthe previous block. Each block also includes a timestamp, its owncryptographic hash, and one or more transactions. The transactions,which have already been verified by the nodes of the blockchain network,are hashed and encoded into a Merkle tree. A Merkle tree is a datastructure in which data at the leaf nodes of the tree is hashed, and allhashes in each branch of the tree are concatenated at the root of thebranch. This process continues up the tree to the root of the entiretree, which stores a hash that is representative of all data in thetree. A hash purporting to be of a transaction stored in the tree can bequickly verified by determining whether it is consistent with thestructure of the tree.

Whereas a blockchain is a decentralized or at least partiallydecentralized data structure for storing transactions, a blockchainnetwork is a network of computing nodes that manage, update, andmaintain one or more blockchains by broadcasting, verifying andvalidating transactions, etc. As introduced above, a blockchain networkcan be provided as a public blockchain network, a private blockchainnetwork, or a consortium blockchain network. Embodiments of thisspecification are described in further detail herein with reference to aconsortium blockchain network. It is contemplated, however, thatembodiments of this specification can be realized in any appropriatetype of blockchain network.

In general, a consortium blockchain network is private among theparticipating entities. In a consortium blockchain network, theconsensus process is controlled by an authorized set of nodes, which canbe referred to as consensus nodes, one or more consensus nodes beingoperated by a respective entity (e.g., a financial institution,insurance company). For example, a consortium of ten (10) entities(e.g., financial institutions, insurance companies) can operate aconsortium blockchain network, each of which operates at least one nodein the consortium blockchain network.

In some examples, within a consortium blockchain network, a globalblockchain is provided as a blockchain that is replicated across allnodes. That is, all consensus nodes are in perfect state consensus withrespect to the global blockchain. To achieve consensus (e.g., agreementto the addition of a block to a blockchain), a consensus protocol isimplemented within the consortium blockchain network. For example, theconsortium blockchain network can implement a practical Byzantine faulttolerance (PBFT) consensus, described in further detail below.

FIG. 1 is a diagram illustrating an example of an environment 100 thatcan be used to execute embodiments of this specification. In someexamples, the environment 100 enables entities to participate in aconsortium blockchain network 102. The environment 100 includescomputing devices 106, 108, and a network 110. In some examples, thenetwork 110 includes a local area network (LAN), wide area network(WAN), the Internet, or a combination thereof, and connects web sites,user devices (e.g., computing devices), and back-end systems. In someexamples, the network 110 can be accessed over a wired and/or a wirelesscommunications link. In some examples, the network 110 enablescommunication with, and within the consortium blockchain network 102. Ingeneral, the network 110 represents one or more communication networks.In some cases, the computing devices 106, 108 can be nodes of a cloudcomputing system (not shown), or each computing device 106, 108 can be aseparate cloud computing system including a number of computersinterconnected by a network and functioning as a distributed processingsystem.

In the depicted example, the computing systems 106, 108 can each includeany appropriate computing system that enables participation as a node inthe consortium blockchain network 102. Examples of computing devicesinclude, without limitation, a server, a desktop computer, a laptopcomputer, a tablet computing device, and a smartphone. In some examples,the computing systems 106, 108 host one or more computer-implementedservices for interacting with the consortium blockchain network 102. Forexample, the computing system 106 can host computer-implemented servicesof a first entity (e.g., user A), such as a transaction managementsystem that the first entity uses to manage its transactions with one ormore other entities (e.g., other users). The computing system 108 canhost computer-implemented services of a second entity (e.g., user B),such as a transaction management system that the second entity uses tomanage its transactions with one or more other entities (e.g., otherusers). In the example of FIG. 1, the consortium blockchain network 102is represented as a peer-to-peer network of nodes, and the computingsystems 106, 108 provide nodes of the first entity, and second entityrespectively, which participate in the consortium blockchain network102.

FIG. 2 depicts an example of an architecture 200 in accordance withembodiments of this specification. The example conceptual architecture200 includes participant systems 202, 204, 206 that correspond toParticipant A, Participant B, and Participant C, respectively. Eachparticipant (e.g., user, enterprise) participates in a blockchainnetwork 212 provided as a peer-to-peer network including a plurality ofnodes 214, at least some of which immutably record information in ablockchain 216. Although a single blockchain 216 is schematicallydepicted within the blockchain network 212, multiple copies of theblockchain 216 are provided, and are maintained across the blockchainnetwork 212, as described in further detail herein.

In the depicted example, each participant system 202, 204, 206 isprovided by, or on behalf of Participant A, Participant B, andParticipant C, respectively, and functions as a respective node 214within the blockchain network. As used herein, a node generally refersto an individual system (e.g., computer, server) that is connected tothe blockchain network 212, and enables a respective participant toparticipate in the blockchain network. In the example of FIG. 2, aparticipant corresponds to each node 214. It is contemplated, however,that a participant can operate multiple nodes 214 within the blockchainnetwork 212, and/or multiple participants can share a node 214. In someexamples, the participant systems 202, 204, 206 communicate with, orthrough the blockchain network 212 using a protocol (e.g., hypertexttransfer protocol secure (HTTPS)), and/or using remote procedure calls(RPCs).

Nodes 214 can have varying degrees of participation within theblockchain network 212. For example, some nodes 214 can participate inthe consensus process (e.g., as miner nodes that add blocks to theblockchain 216), while other nodes 214 do not participate in theconsensus process. As another example, some nodes 214 store a completecopy of the blockchain 216, while other nodes 214 only store copies ofportions of the blockchain 216. For example, data access privileges canlimit the blockchain data that a respective participant stores withinits respective system. In the example of FIG. 2, the participant systems202, 204, and 206 store respective, complete copies 216′, 216″, and216′″ of the blockchain 216.

A blockchain (e.g., the blockchain 216 of FIG. 2) is made up of a chainof blocks, each block storing data. Examples of data include transactiondata representative of a transaction between two or more participants.While transactions are used herein by way of non-limiting example, it iscontemplated that any appropriate data can be stored in a blockchain(e.g., documents, images, videos, audio). Examples of a transaction caninclude, without limitation, exchanges of something of value (e.g.,assets, products, services, currency). The transaction data is immutablystored within the blockchain. That is, the transaction data cannot bechanged.

Before storing in a block, the transaction data is hashed. Hashing is aprocess of transforming the transaction data (provided as string data)into a fixed-length hash value (also provided as string data). It is notpossible to un-hash the hash value to obtain the transaction data.Hashing ensures that even a slight change in the transaction dataresults in a completely different hash value. Further, and as notedabove, the hash value is of fixed length. That is, no matter the size ofthe transaction data the length of the hash value is fixed. Hashingincludes processing the transaction data through a hash function togenerate the hash value. An example of a hash function includes, withoutlimitation, the secure hash algorithm (SHA)-256, which outputs 256-bithash values.

Transaction data of multiple transactions are hashed and stored in ablock. For example, hash values of two transactions are provided, andare themselves hashed to provide another hash. This process is repeateduntil, for all transactions to be stored in a block, a single hash valueis provided. This hash value is referred to as a Merkle root hash, andis stored in a header of the block. A change in any of the transactionswill result in change in its hash value, and ultimately, a change in theMerkle root hash.

Blocks are added to the blockchain through a consensus protocol.Multiple nodes within the blockchain network participate in theconsensus protocol, and perform work to have a block added to theblockchain. Such nodes are referred to as consensus nodes. PBFT,introduced above, is used as a non-limiting example of a consensusprotocol. The consensus nodes execute the consensus protocol to addtransactions to the blockchain, and update the overall state of theblockchain network.

In further detail, the consensus node generates a block header, hashesall of the transactions in the block, and combines the hash value inpairs to generate further hash values until a single hash value isprovided for all transactions in the block (the Merkle root hash). Thishash is added to the block header. The consensus node also determinesthe hash value of the most recent block in the blockchain (i.e., thelast block added to the blockchain). The consensus node also adds anonce value, and a timestamp to the block header.

In general, PBFT provides a practical Byzantine state machinereplication that tolerates Byzantine faults (e.g., malfunctioning nodes,malicious nodes). This is achieved in PBFT by assuming that faults willoccur (e.g., assuming the existence of independent node failures, and/ormanipulated messages sent by consensus nodes). In PBFT, the consensusnodes are provided in a sequence that includes a primary consensus node,and backup consensus nodes. The primary consensus node is periodicallychanged. Transactions are added to the blockchain by all consensus nodeswithin the blockchain network reaching an agreement as to the worldstate of the blockchain network. In this process, messages aretransmitted between consensus nodes, and each consensus nodes provesthat a message is received from a specified peer node, and verifies thatthe message was not modified during transmission.

In PBFT, the consensus protocol is provided in multiple phases with allconsensus nodes beginning in the same state. To begin, a client sends arequest to the primary consensus node to invoke a service operation(e.g., execute a transaction within the blockchain network). In responseto receiving the request, the primary consensus node multicasts therequest to the backup consensus nodes. The backup consensus nodesexecute the request, and each sends a reply to the client. The clientwaits until a threshold number of replies are received. In someexamples, the client waits for f+1 replies to be received, where f isthe maximum number of faulty consensus nodes that can be toleratedwithin the blockchain network. The final result is that a sufficientnumber of consensus nodes come to an agreement on the order of therecord that is to be added to the blockchain, and the record is eitheraccepted, or rejected.

In some blockchain networks, cryptography is implemented to maintainprivacy of transactions. For example, if two nodes want to keep atransaction private, such that other nodes in the blockchain networkcannot discern details of the transaction, the nodes can encrypt thetransaction data. An example of cryptography includes, withoutlimitation, symmetric encryption, and asymmetric encryption. Symmetricencryption refers to an encryption process that uses a single key forboth encryption (generating ciphertext from plaintext), and decryption(generating plaintext from ciphertext). In symmetric encryption, thesame key is available to multiple nodes, so each node can en-/de-crypttransaction data.

Asymmetric encryption uses keys pairs that each include a private key,and a public key, the private key being known only to a respective node,and the public key being known to any or all other nodes in theblockchain network. A node can use the public key of another node toencrypt data, and the encrypted data can be decrypted using other node'sprivate key. For example, and referring again to FIG. 2, Participant Acan use Participant B's public key to encrypt data, and send theencrypted data to Participant B. Participant B can use its private keyto decrypt the encrypted data (ciphertext) and extract the original data(plaintext). Messages encrypted with a node's public key can only bedecrypted using the node's private key.

Asymmetric encryption is used to provide digital signatures, whichenables participants in a transaction to confirm other participants inthe transaction, as well as the validity of the transaction. Forexample, a node can digitally sign a message, and another node canconfirm that the message was sent by the node based on the digitalsignature of Participant A. Digital signatures can also be used toensure that messages are not tampered with in transit. For example, andagain referencing FIG. 2, Participant A is to send a message toParticipant B. Participant A generates a hash of the message, and then,using its private key, encrypts the hash to provide a digital signatureas the encrypted hash. Participant A appends the digital signature tothe message, and sends the message with digital signature to ParticipantB. Participant B decrypts the digital signature using the public key ofParticipant A, and extracts the hash. Participant B hashes the messageand compares the hashes. If the hashes are same, Participant B canconfirm that the message was indeed from Participant A, and was nottampered with.

As described earlier, blockchain networks can store different types ofdata such as state data, block data, and index data. State data areoften stored as a content-addressed state tree (e.g., MPT or FDMT).Content-addressed state trees are incremental in nature. That is,changes of account states are reflected by adding new tree structuresinstead of updating the existing state tree. Therefore, thecontent-addressed state trees can grow very large in size when blocksare continuously added to the blockchain. On the other hand, most datain the trees are infrequently used historic state data. Storing thosehistoric state data in every blockchain node can be quite inefficient interms of storage resource usage.

Under the FDMT storage scheme, state data can be separated into currentstate data associated with the current block and historic state dataassociated with all blocks of the blockchain. To save on storageresources without materially affecting computational efficiency, thehistoric state data can be stored on one or more trusted storagelocations or one or more shared storage nodes elected through voting.Access of the historic state data can then be shared by other nodes ofthe blockchain network.

In addition to sharing historic state data, block data may also beshared. Instead of storing every transaction and block generated on theblockchain, regular consensus nodes can store block headers instead ofentire blocks. The consensus nodes can inquire the shared storage nodesthat store the entire blocks when verification of blockchaintransactions are needed. Since the consensus nodes store the currentstate data associated with the current block, such data can be used forexecuting smart contract. Therefore, by sharing historic state data andblock data, the storage consumption of the blockchain network can bereduced without significant compromising processing efficiency oftransactions.

FIG. 3 depicts an example of an FDMT data structure 300 in accordancewith embodiments of this specification. Under FDMT, account states canbe stored as KVPs in the structures of a historic state tree 302 and acurrent state tree 304. The keys correspond to addresses that uniquelyidentify values of blockchain accounts. The historic state tree 302 caninclude an entire copy of available state information of the blockchain.The current state tree 304 can include state information of a currentblock. Therefore, the size of the current state tree 304 can besignificantly smaller than the size of the historic state tree 302.

In some embodiments, the current state tree 304 can be alocation-addressed state tree. For a location-addressed state tree, anode value of the current state tree 304 can be retrieved based on a keythat uniquely identifies the node (i.e., a node ID). When new node isadded to the current state tree 304, node value can be associated withits unique node ID (e.g., ID 1-1, ID 2-1, etc. of the current state tree304) without regard to its content. In some cases, a KVP of the currentstate tree 304 can be expressed as <node ID, node value>. In some cases,the keys of the KVPs can further include a corresponding block ID of thenode value. In such cases, the node ID can serve as prefix and the blockID can serve us suffix of keys. The KVP of the current state tree 304can then be expressed as <node ID+block ID, node value>.

In some embodiments, the historic state tree 302 can be acontent-addressed state tree. For a content-addressed state tree, eachaccount value can have a content address uniquely associated with thevalue to the information content itself. To retrieve information from ahistoric state tree 302, a content identifier can be provided, fromwhich the location of the account value can be determined and retrieved.Similar to MPT, each node of the historic state tree 302 can include ahash value of a pointer (e.g., Hash1, Hash2, and Hash3 under thehistoric state tree 302) pointing to the next node of the tree.Following paths of the pointers, the last elements stores hash values ofend portion of the keys (e.g., Hash4, Hash5, Hash6, and Hash7 under thehistoric state tree 302) and the values that the keys are paired with.KVPs of the historic state tree 302 can be expressed as <hash(nodevalue), node value>.

Since node addresses of content-addressed trees are dependent on nodevalues, new state information can be added as additional tree structureto the historic state tree 302 rather than making changes to theexisting tree to preserve tree structure and improve datastorage/retrieval efficiency.

FIG. 4 depicts examples of databases 400 for storing blockchain data inaccordance with embodiments of this specification. The databases 400 canbe key-value databases such as levelDB or RocksDB. The databases 400 canstore data under the FDMT data structure, which includes historydatabase 410 for storing historic state tree and current database 412for storing current state tree. For the four blocks depicted in FIG. 4,block i−2 402, block i−1 404, and block i 406 are previously completedblocks. Block i+1 408 is a current block. Each block can have a blockheader and a block body. The block header can include information suchas a root hash of the world state. The root hash can serve as a secureand unique identifier for the state trees. In other words, the root hashcan be cryptographically dependent on account states. The block body caninclude confirmed transactions of the corresponding block.

The history database 410 can store the historic state tree. The currentdatabase 412 can store the current state tree. The historic state treeand current state tree can store historical and current account states.Ethereum blockchain accounts can include externally owned accounts andcontract accounts. Externally owned accounts can be controlled byprivate keys and are not associated with any code for executing smartcontract. Contract accounts can be controlled by their contract code areassociated with code for executing smart contract.

States of Ethereum accounts can include four components: nonce, balance,codeHash, and storageRoot. If the account is an externally ownedaccount, the nonce can represent the number of transactions sent fromthe account address. The balance can represent the digital assets ownedby the account. The codeHash can be the hash of an empty string. ThestorageRoot can be empty. If the account is a contract account, thenonce can represent the number of contracts created by the account. Thebalance can represent the digital assets owned by the account. ThecodeHash can be the hash of a virtual machine code associated with theaccount. The storageRoot can store a root hash associated with a storagetree. The storage tree can store contract data by encoding the hash ofthe storage contents of the account.

The historic state tree can include an entire copy of account states ofthe blockchain from the genesis block, and can be updated according totransaction executions. For example, root hash stored in previous blocki−1 404 is a root hash of the world state at the time block i−1 404 iscompleted. The world state is associated with all transactions stored inblock i−1 404 and blocks prior to block i−1 404. Similarly, root hashstored in the current block i+1 408 is a root hash of the world stateassociated with all transactions stored in block i+1 408 and blocksprior to block i+1 408.

The current state tree can include state information that is updated oradded due to transactions newly added to the current block i+1 408. Asdiscussed in the description of FIG. 3, the historic state tree canstore state information as KVPs expressed as <hash(node value), nodevalue>, which is content-addressable. In some embodiments, the currentstate tree can be location-addressed based on one or more locationrelated IDs. For example, the current state tree can store stateinformation as KVPs expressed as <node ID, node value>, where the nodevalues can be addressed based on their corresponding node IDs. Asanother example, the keys of the KVPs can be a combination of the nodeID and the corresponding block ID of the node value. The node ID canserve as prefix and the block ID can serve us suffix of keys fortraversing values of an FDMT or MPT.

FIG. 5 depicts an example of a blockchain network 500 using sharedstorage in accordance with embodiments of this specification. At ahigh-level, the blockchain network 500 includes a plurality of consensusnodes 506, 508, 510, and 512, a shared storage node 502, and a cloudstorage 504 communicably coupled to the shared storage node 502. Theshared storage node 502 can be a node with proof of authority (POA). Insome cases, the POA can be provided based on the status of the sharedstorage node 506. For example, the shared storage node 506 can be a nodeadministered by a deployer of the blockchain network 500. In such cases,the shared storage node 502 can be part of the blockchain network 500 oroutside of the blockchain network 500. In some cases, the POA can begained through voting. For example, assume that the blockchain networkincludes 3f+1 nodes (f=1 in the example as depicted in FIG. 5, when theshared storage node 502 participates in consensus of the blockchainnetwork 500), the maximum faulty consensus nodes or Byzantine nodes(nodes that fail to act or act maliciously) that can be tolerated is f.As such, if 2f+1 nodes cast votes (endorsed by their respective digitalsignatures) to elect the shared storage node 502, the votes 2f+1 can beused as POA for trusting the shared storage node 502.

As described in the discussion of FIG. 4, under the FDMT data structure,current state data can be separated from the state data. The currentstate data can be stored as a current state tree, which includes stateinformation associated with a current block, such as state data updatedor added according to transactions newly added to the current block. Inan Ethereum type system, state information associated with the currentblock can be considered as “hot” data, frequently retrieved by a virtualmachine to execute smart contracts. Historic state data can be stored asa historic state tree, which can include an entire copy of accountstates of the blockchain from the genesis block. State informationassociated with previous blocks stored in the historic state tree can beconsidered as “cold” data, which are visited less often for executingsmart contract.

Data in a content-addressed state tree (e.g., MPT or the historic state)are incremental in nature. That is, changes of account states due toadditions of new blocks do not change existing historic states, but arereflected by adding new tree structures to the historic state tree.Therefore, historic state tree can grow very large in size due togenerations of new blocks. Because most data in the historic state treeare “cold” data that are infrequently used, storing those data in everyblockchain node can be quite inefficient in terms of usage of storageresources.

To save on storage resources without significantly compromisingcomputational efficiency, the historic state tree can be stored on ahistory database (such as the history database 410 described in FIG. 4)associated with a shared storage node 502 or a cloud storage 504communicably coupled to the shared storage node 502. In someembodiments, the shared storage node 502 can share access of thehistoric state tree to the consensus nodes 506, 508, 510, and 512. Thecloud storage 504 can be a storage device that provides storage serviceon the cloud, such as a network attached storage (NAS) or object storageservice (OSS).

In some embodiments, when transactions are processed into a currentblock, state data associated with the transactions can be sent by one ormore of the consensus nodes 506, 508, 510, and 512 to the shared storagenode 502 for storage. In some embodiments, the one or more of theconsensus nodes 506, 508, 510, and 512 can send the state data and ahash value of the state data as a KVP to the shared storage node 502.After receiving the state data or the KVP, the shared storage node 502can verify if the received state data or the KVP has already beenlocally stored or stored in the cloud storage 504. If yes, the sharedstorage node 502 can reject or abandon the received state data.Otherwise, the shared storage node 502 can calculate a hash value of thestate data or verify that the received hash value is the hash value ofthe state data, and store the hash value and the state data to thehistoric state tree.

In some embodiments, the shared storage node 502 can verify whether thestate data are valid state data of the blockchain. The shared storagenode 502 can calculate a hash value of the received state data. Asdiscussed earlier, the shared storage node 502 can store the historicstate tree, which is content-addressed and includes an entire copy ofstate information of the blockchain. The calculated hash value can thenbe used for verifying whether the state data is part of the blockchainbased on the world state root hash of the blockchain (e.g., using Merkleproof). If the hash value is verified as part of the blockchain, thestate data can be determined as content-addressed data.

When any one of the consensus nodes 506, 508, 510, and 512 needs toretrieve state data from the shared storage node 502, a correspondinghash value can be sent to the shared storage node 502. Since thehistoric state tree stored in the shared storage node 502 iscontent-addressed, the hash value can be used as key for addressing thecorresponding state data that produces the hash value. After identifyingthe corresponding state data based on the hash value, the shared storagenode 502 can send the identified state data back to the consensus node.The consensus node receiving the state data can hash the received statedata to verify whether the state data is content-addressed. If yes, thestate data can be determined as authentic. Otherwise, the state data isunauthentic. If the state data is unauthentic, the consensus node canchoose to report the shared storage node 502 as a faulty node (or aByzantine node). If there are other nodes in the blockchain network 500that store the historic state tree, the consensus node can send the hashvalue to one or more of the other nodes to retrieve the correspondingstate data.

FIG. 6 depicts another example of a blockchain network 600 using sharedstorage in accordance with embodiments of this specification. At ahigh-level, the blockchain network 600 includes a plurality of consensusnodes 606, 608, 610, and 612, a plurality of shared storage nodes 602and 604, and a cloud storage 614 communicably coupled to one or more ofthe plurality of shared storage nodes 602 and 604. In some cases, theshared storage nodes 602 and 604 can be nodes with POA, such as nodesbeing administered by a deployer of the blockchain network 600. In suchcases, the shared storage nodes 602 and 604 can be part of theblockchain network 600 or outside of the blockchain network 600. In somecases, the POA can be gained through voting. For example, assume thatthe blockchain network includes 3f+1 nodes (f=1 in the example asdepicted in FIG. 6, when none of the shared storage nodes 602 and 604participates in the consensus of the blockchain network 600), 3f+2 nodes(when one of the shared storage nodes 602 and 604 participates in theconsensus of the blockchain network 600), or 3f+3 nodes (when both ofthe shared storage nodes 602 and 604 participate in the consensus of theblockchain network), where f is the maximum number of Byzantine nodes,if 2f+1 nodes cast votes (endorsed by their respective digitalsignatures) to elect a consensus node as a shared storage node, the 2f+1votes can be used as POA for trusting the shared storage node.

As discussed earlier, to save on storage resources without significantlysacrificing computational efficiency, the historic state tree can bestored on a history database (such as the history database 410 describedin FIG. 4) associated with the shared storage nodes 602 and 604 or thecloud storage 614 communicably coupled to the shared storage nodes 602and 604. The shared storage nodes 602 and 604 can share access of thehistoric state tree to the consensus nodes 606, 608, 610, and 612. Thecloud storage 614 can be a storage device that can provide storageservice on the cloud, such as an NAS or OSS.

When transactions are processed into a current block, state dataassociated with the transactions can be sent by one or more of theconsensus nodes 606, 608, 610, and 612 to the shared storage nodes 602and 604 for storage. In some embodiments, the one or more of theconsensus nodes 606, 608, 610, and 612 can send the state data and ahash value of the state data as a KVP to the shared storage nodes 602and 604. After receiving the state data, the shared storage nodes 602and 604 can verify if the received state data or KVP has already beenlocally stored or stored in the cloud storage 614. If yes, the sharedstorage nodes 602 and 604 can reject or abandon the received state data.Otherwise, the shared storage nodes 602 and 604 can calculate a hashvalue of the state data or verify that the received hash value is thehash value of the state data, and store the hash value and the statedata to the historic state tree.

In some embodiments, the shared storage nodes 602 and 604 can verifywhether the state data are valid state data of the blockchain. Asdiscussed earlier, the shared storage nodes 602 and 604 can store thehistoric state tree, which is content-addressed and includes an entirecopy of state information of the blockchain. The shared storage nodes602 and 604 can calculate a hash value of the received state data. Thecalculated hash value can then be used for verifying whether the statedata is part of the blockchain based on the world state root hash of theblockchain (e.g., using Merkle proof). If yes, the state data can bedetermined as content-addressed.

When any one of the consensus nodes 606, 608, 610, and 612 needs toretrieve state data from the shared storage node 602 or 604, acorresponding hash value can be sent to a shared storage node that theconsensus node is in communication with. As shown in the exampledepicted in FIG. 6, consensus nodes 606 and 608 can send the hash valueto storage node 602, consensus nodes 610 and 612 can send the hash valueto storage node 604. A consensus node can select shared storage node forretrieving state data from based on geographic proximity, networkcondition, established communication protocol, security consideration,etc. It is to be understood that any of the consensus nodes 606, 608,610, and 612 can choose to communicate with any of the shared storagenodes 602 and 604, according to different embodiments of the presentspecification.

Since the historic state tree stored in the shared storage nodes 602 and604 is content-addressed, the hash value can be used as key foraddressing the corresponding state data. After identifying thecorresponding state data based on the hash value, the correspondingshared storage node 602 or 604 can send the identified state data backto the consensus node. The consensus node receiving the state data canhash the received state data to verify whether the state data iscontent-addressed. If yes, the state data is determined as authentic.Otherwise, the state data is unauthentic. If the state data isunauthentic, the consensus node can choose to report the shared storagenode as a faulty node (or a Byzantine node). If there are other nodes inthe blockchain network 600 that store the historic state tree, theconsensus node can send the hash value to one or more of the other nodesto retrieve the corresponding state data.

FIG. 7 depicts yet another example of a blockchain network 700 usingshared storage in accordance with embodiments of this specification. Ata high-level, the blockchain network 700 includes a plurality ofconsensus nodes 706, 708, 710, and 712, a plurality of shared storagenodes 702 and 704, and a cloud storage 714 communicably coupled to oneor more of the plurality of shared storage nodes 702 and 704. The sharedstorage nodes 702 and 704 can be nodes with POA, such as nodes beingadministered by a deployer of the blockchain network 700. In such cases,the shared storage nodes 702 and 704 can be part of the blockchainnetwork 700 or outside of the blockchain network 700. As describedearlier, the POA can also be gained through voting. For example, assumethat the blockchain network includes 3f+1 nodes (f=1 in the example asdepicted in FIG. 7, when none of the shared storage nodes 702 and 704participates in the consensus of the blockchain network 700), 3f+2 nodes(when one of the shared storage nodes 702 and 704 participates in theconsensus of the blockchain network 700), or 3f+3 nodes (when both ofthe shared storage nodes 702 and 704 participate in the consensus of theblockchain network), where f is the maximum number of Byzantine nodes,if 2f+1 nodes cast votes (endorsed by their respective digitalsignatures) to elect a consensus node as a shared storage node, the 2f+1votes can be used as POA for trusting the shared storage node.

To save on storage resources without significantly compromisingcomputational efficiency, the historic state tree can be stored on ahistory database (such as the history database 410 described in FIG. 4)associated with the shared storage nodes 702, 704 or a cloud storage(e.g., NAS or OSS). The shared storage nodes 702 and 704 can shareaccess of the historic state tree to the consensus nodes 706, 708, 710,and 712.

In some embodiments, in addition to sharing historic state data from theshared storage nodes 702 and 704, block data can also be shared. Similarto full nodes of a blockchain network, shared storage nodes 702 and 704can store an entire copy of the blockchain, which includes everytransaction and block generated on the blockchain. In some embodiments,the shared storage nodes 702 and 704 can store block body of every blockof the blockchain. Similar to light weight nodes of a blockchainnetwork, the consensus nodes 706, 708, 710, and 712 can store blockheader of every block of the blockchain, based on methods such as thesimplified payment verification (SPV). SPV can allow a node to verify ifa transaction has been included in a block, without having to downloadthe entire blockchain. Since the consensus nodes 706, 708, 710, and 712also store the current state tree, state data associated with thecurrent block can be used for executing smart contract. As such, bysharing block data from the shared storage nodes 702 and 704, thestorage consumption of the consensus nodes 706, 708, 710, and 712 can befurther reduced while maintaining the ability to directly execute smartcontract.

FIG. 8 is a flowchart of an example of a process 800 for communicatingand sharing blockchain data. For convenience, the process 800 will bedescribed as being performed by a system of one or more computers,located in one or more locations, and programmed appropriately inaccordance with this specification. For example, a computing device in acomputing system, e.g., the computing system 106, 108 of FIG. 1,appropriately programmed, can perform the process 800.

At 802, a consensus node of a blockchain network sends current stateinformation associated with a current block of a blockchain to one ormore shared storage nodes of the blockchain network, wherein theconsensus node stores the current state information and the one or moreshared storage nodes store historic state information associated withevery block of the blockchain as a historic state tree, and wherein thehistoric state tree includes KVPs with values being account states ofaccounts associated with the blockchain network and keys being hashvalues of the corresponding account states.

At 804, the consensus node sends a hash value to the one of the one ormore shared storage nodes for retrieving an account state stored in thehistoric state tree.

At 806, the consensus node receives the account state in response tosending the hash value.

At 808, the consensus node verifies that the account state is part ofthe blockchain based on the hash value.

In some cases, the blockchain network includes at least f+1 sharedstorage nodes and no more than 2f+2 consensus nodes, and wherein f isthe maximum number of faulty shared storage nodes and consensus nodesthat can be tolerated within the blockchain network.

In some cases, the one or more shared storage nodes are elected byreceiving 2f+1 votes from all 3f+1, 3f+2, or 3f+3 nodes of theblockchain network, and wherein f is the maximum number of faulty sharedstorage nodes and consensus nodes that can be tolerated within theblockchain.

In some cases, the current state tree includes KVPs with values beingaccount sates associated with the current block and keys being node IDscorresponding to nodes of the current state tree and a block IDcorresponding to the current block.

In some cases, the current state information sent by the consensus nodeincludes a digital signature generated based on a private key associatedwith the consensus node.

In some cases, sending the current state information further comprisessending the current state information and a hash value of the currentstate information as KVP to the one or more shared storage nodes of theblockchain network.

In some cases, verifying that the account state is part of theblockchain is performed based on hashing the account state to generate ahashed account state and comparing the hashed account state to the hashvalue.

In some cases, the one or more shared storage nodes store historic stateinformation locally or on a cloud storage.

In some cases, the current state tree and the historic state tree arestored as a fixed depth Merkle tree.

FIG. 9 is a diagram of on example of modules of an apparatus 900 inaccordance with embodiments of this specification.

The apparatus 900 can be an example of an embodiment of a consensus nodeconfigured to communicate and share blockchain data. The apparatus 900can correspond to the embodiments described above, and the apparatus 900includes the following: a sending module 902 that sends current stateinformation associated with a current block of a blockchain to one ormore shared storage nodes of the blockchain network, wherein theconsensus node stores the current state information and the one or moreshared storage nodes store historic state information associated withevery block of the blockchain as a historic state tree, and wherein thehistoric state tree includes KVPs with values being account states ofaccounts associated with the blockchain network and keys being hashvalues of the corresponding account states; the sending module 902 thatsends a hash value to the one of the one or more shared storage nodesfor retrieving an account state stored in the historic state tree; areceiving module 904 that receives the account state in response tosending the hash value; and a verifying module 906 that verifies theaccount state is part of the blockchain based on the hash value.

In an optional embodiment, the apparatus 900 further includes thefollowing: the blockchain network includes at least f+1 shared storagenodes and no more than 2f+2 consensus nodes, and wherein f is themaximum number of faulty shared storage nodes and consensus nodes thatcan be tolerated within the blockchain network.

In an optional embodiment, the one or more shared storage nodes areelected by receiving 2f+1 votes from all 3f+1, 3f+2, or 3f+3 nodes ofthe blockchain network, and wherein f is the maximum number of faultyshared storage nodes and consensus nodes that can be tolerated withinthe blockchain.

In an optional embodiment, the current state tree includes KVPs withvalues being account sates associated with the current block and keysbeing node IDs corresponding to nodes of the current state tree and ablock ID corresponding to the current block.

In an optional embodiment, the current state information sent by theconsensus node includes a digital signature generated based on a privatekey associated with the consensus node.

In an optional embodiment, sending the current state information furthercomprises sending the current state information and a hash value of thecurrent state information as KVP to the one or more shared storage nodesof the blockchain network.

In an optional embodiment, verifying that the account state is part ofthe blockchain is performed based on hashing the account state togenerate a hashed account state and comparing the hashed account stateto the hash value.

In an optional embodiment, the one or more shared storage nodes storehistoric state information locally or on a cloud storage.

In an optional embodiment, the current state tree and the historic statetree are stored as a fixed depth Merkle tree.

The system, apparatus, module, or unit illustrated in the previousembodiments can be implemented by using a computer chip or an entity, orcan be implemented by using a product having a certain function. Atypical embodiment device is a computer, and the computer can be apersonal computer, a laptop computer, a cellular phone, a camera phone,a smartphone, a personal digital assistant, a media player, a navigationdevice, an email receiving and sending device, a game console, a tabletcomputer, a wearable device, or any combination of these devices.

For an embodiment process of functions and roles of each module in theapparatus, references can be made to an embodiment process ofcorresponding steps in the previous method. Details are omitted here forsimplicity.

Because an apparatus embodiment basically corresponds to a methodembodiment, for related parts, references can be made to relateddescriptions in the method embodiment. The previously describedapparatus embodiment is merely an example. The modules described asseparate parts may or may not be physically separate, and partsdisplayed as modules may or may not be physical modules, may be locatedin one position, or may be distributed on a number of network modules.Some or all of the modules can be selected based on actual demands toachieve the objectives of the solutions of the specification. A personof ordinary skill in the art can understand and implement theembodiments of the present application without creative efforts.

Referring again to FIG. 9, it can be interpreted as illustrating aninternal functional module and a structure of a consensus node. Anexecution body in essence can be an electronic device, and theelectronic device includes the following: one or more processors; andone or more computer-readable memories configured to store an executableinstruction of the one or more processors. In some embodiments, the oneor more computer-readable memories are coupled to the one or moreprocessors and have programming instructions stored thereon that areexecutable by the one or more processors to perform algorithms, methods,functions, processes, flows, and procedures, as described in thisspecification.

The techniques described in this specification produce several technicaleffects. For example, embodiments of the subject matter can allowsavings of storage resources of blockchain nodes without significantlysacrificing computational efficiency. Because most data in the historicstate tree are “cold” data that are infrequently used, by saving the“cold” data only in the shared storage nodes, usage rate of storagespace across the blockchain network can be significantly improved. Ifthe share storage node is a POA node or elected by voting based on PBFTconsensus, the historic state tree only needs to be stored in the sharestorage node instead of storing on every blockchain node. If sharedstorage nodes are part of the blockchain consensus nodes without POA,for an N consensus nodes blockchain network, where N equals 3f+1, 3f+2,or 3f+3, where f is the number of maximum faulty consensus nodes,(N−f−1)/N of the blockchain consensus nodes only need to store “hot”data as a current state tree, instead of both “cold” and “hot” data asthe historic state tree.

Moreover, for the N consensus nodes blockchain network where f+1 nodesare used as shared storage nodes to store the historic state tree, amaximum off faulty consensus nodes can be tolerated. In other words, thesaving of storage space does not compromise data reliability. Theconsensus nodes of the blockchain network can be properly served bytolerating f faulty consensus nodes and saving the entire copy ofblockchain only on f+1 nodes. Because the reliability of the system isensured by the f+1 shared storage node, data security can be improvedand relatively independent from the security level of the underlyingservice platform.

Described embodiments of the subject matter can include one or morefeatures, alone or in combination.

For example, in a first embodiment, a computer-implemented method forcommunicating shared blockchain data, the method comprising: sending, bya consensus node of a blockchain network, current state informationassociated with a current block of a blockchain to one or more sharedstorage nodes of the blockchain network, wherein the consensus nodestores the current state information and the one or more shared storagenodes store historic state information associated with every block ofthe blockchain as a historic state tree, and wherein the historic statetree includes KVPs with values being account states of accountsassociated with the blockchain network and keys being hash values of thecorresponding account states; sending, by the consensus node, a hashvalue to the one of the one or more shared storage nodes for retrievingan account state stored in the historic state tree; receiving, by theconsensus node, the account state in response to sending the hash value;and verifying, by the consensus node, that the account state is part ofthe blockchain based on the hash value.

The foregoing and other described embodiments can each, optionally,include one or more of the following features:

A first feature, combinable with any of the following features,specifies that the blockchain network includes at least f+1 sharedstorage nodes and no more than 2f+2 consensus nodes, and wherein f isthe maximum number of faulty shared storage nodes and consensus nodesthat can be tolerated within the blockchain network.

A second feature, combinable with any of the previous or followingfeatures, specifies that the one or more shared storage nodes areelected by receiving 2f+1 votes from all 3f+1, 3f+2, or 3f+3 nodes ofthe blockchain network, and wherein f is the maximum number of faultyshared storage nodes and consensus nodes that can be tolerated withinthe blockchain.

A third feature, combinable with any of the previous or followingfeatures, specifies that the current state tree includes KVPs withvalues being account sates associated with the current block and keysbeing node IDs corresponding to nodes of the current state tree and ablock ID corresponding to the current block.

A fourth feature, combinable with any of the previous or followingfeatures, specifies that the current state information sent by theconsensus node includes a digital signature generated based on a privatekey associated with the consensus node.

A fifth feature, combinable with any of the previous or followingfeatures, specifies that sending the current state information furthercomprises sending the current state information and a hash value of thecurrent state information as KVP to the one or more shared storage nodesof the blockchain network.

A sixth feature, combinable with any of the previous or followingfeatures, specifies that verifying that the account state is part of theblockchain is performed based on hashing the account state to generate ahashed account state and comparing the hashed account state to the hashvalue.

A seventh feature, combinable with any of the previous or followingfeatures, specifies that the one or more shared storage nodes storehistoric state information locally or on a cloud storage.

An eighth feature, combinable with any of the previous or followingfeatures, specifies that the current state tree and the historic statetree are stored as a fixed depth Merkle tree.

Embodiments of the subject matter and the actions and operationsdescribed in this specification can be implemented in digital electroniccircuitry, in tangibly-embodied computer software or firmware, incomputer hardware, including the structures disclosed in thisspecification and their structural equivalents, or in combinations ofone or more of them. Embodiments of the subject matter described in thisspecification can be implemented as one or more computer programs, e.g.,one or more modules of computer program instructions, encoded on acomputer program carrier, for execution by, or to control the operationof, data processing apparatus. For example, a computer program carriercan include one or more computer-readable storage media that haveinstructions encoded or stored thereon. The carrier may be a tangiblenon-transitory computer-readable medium, such as a magnetic, magnetooptical, or optical disk, a solid state drive, a random access memory(RAM), a read-only memory (ROM), or other types of media. Alternatively,or in addition, the carrier may be an artificially generated propagatedsignal, e.g., a machine-generated electrical, optical, orelectromagnetic signal that is generated to encode information fortransmission to suitable receiver apparatus for execution by a dataprocessing apparatus. The computer storage medium can be or be part of amachine-readable storage device, a machine-readable storage substrate, arandom or serial access memory device, or a combination of one or moreof them. A computer storage medium is not a propagated signal.

A computer program, which may also be referred to or described as aprogram, software, a software application, an app, a module, a softwaremodule, an engine, a script, or code, can be written in any form ofprogramming language, including compiled or interpreted languages, ordeclarative or procedural languages; and it can be deployed in any form,including as a stand-alone program or as a module, component, engine,subroutine, or other unit suitable for executing in a computingenvironment, which environment may include one or more computersinterconnected by a data communication network in one or more locations.

A computer program may, but need not, correspond to a file in a filesystem. A computer program can be stored in a portion of a file thatholds other programs or data, e.g., one or more scripts stored in amarkup language document, in a single file dedicated to the program inquestion, or in multiple coordinated files, e.g., files that store oneor more modules, sub programs, or portions of code.

Processors for execution of a computer program include, by way ofexample, both general- and special-purpose microprocessors, and any oneor more processors of any kind of digital computer. Generally, aprocessor will receive the instructions of the computer program forexecution as well as data from a non-transitory computer-readable mediumcoupled to the processor.

The term “data processing apparatus” encompasses all kinds ofapparatuses, devices, and machines for processing data, including by wayof example a programmable processor, a computer, or multiple processorsor computers. Data processing apparatus can include special-purposelogic circuitry, e.g., an FPGA (field programmable gate array), an ASIC(application specific integrated circuit), or a GPU (graphics processingunit). The apparatus can also include, in addition to hardware, codethat creates an execution environment for computer programs, e.g., codethat constitutes processor firmware, a protocol stack, a databasemanagement system, an operating system, or a combination of one or moreof them.

The processes and logic flows described in this specification can beperformed by one or more computers or processors executing one or morecomputer programs to perform operations by operating on input data andgenerating output. The processes and logic flows can also be performedby special-purpose logic circuitry, e.g., an FPGA, an ASIC, or a GPU, orby a combination of special-purpose logic circuitry and one or moreprogrammed computers.

Computers suitable for the execution of a computer program can be basedon general or special-purpose microprocessors or both, or any other kindof central processing unit. Generally, a central processing unit willreceive instructions and data from a read only memory or a random accessmemory or both. Elements of a computer can include a central processingunit for executing instructions and one or more memory devices forstoring instructions and data. The central processing unit and thememory can be supplemented by, or incorporated in, special-purpose logiccircuitry.

Generally, a computer will also include, or be operatively coupled toreceive data from or transfer data to one or more storage devices. Thestorage devices can be, for example, magnetic, magneto optical, oroptical disks, solid state drives, or any other type of non-transitory,computer-readable media. However, a computer need not have such devices.Thus, a computer may be coupled to one or more storage devices, such as,one or more memories, that are local and/or remote. For example, acomputer can include one or more local memories that are integralcomponents of the computer, or the computer can be coupled to one ormore remote memories that are in a cloud network. Moreover, a computercan be embedded in another device, e.g., a mobile telephone, a personaldigital assistant (PDA), a mobile audio or video player, a game console,a Global Positioning System (GPS) receiver, or a portable storagedevice, e.g., a universal serial bus (USB) flash drive, to name just afew.

Components can be “coupled to” each other by being commutatively such aselectrically or optically connected to one another, either directly orvia one or more intermediate components. Components can also be “coupledto” each other if one of the components is integrated into the other.For example, a storage component that is integrated into a processor(e.g., an L2 cache component) is “coupled to” the processor.

To provide for interaction with a user, embodiments of the subjectmatter described in this specification can be implemented on, orconfigured to communicate with, a computer having a display device,e.g., a LCD (liquid crystal display) monitor, for displaying informationto the user, and an input device by which the user can provide input tothe computer, e.g., a keyboard and a pointing device, e.g., a mouse, atrackball or touchpad. Other kinds of devices can be used to provide forinteraction with a user as well; for example, feedback provided to theuser can be any form of sensory feedback, e.g., visual feedback,auditory feedback, or tactile feedback; and input from the user can bereceived in any form, including acoustic, speech, or tactile input. Inaddition, a computer can interact with a user by sending documents toand receiving documents from a device that is used by the user; forexample, by sending web pages to a web browser on a user's device inresponse to requests received from the web browser, or by interactingwith an app running on a user device, e.g., a smartphone or electronictablet. Also, a computer can interact with a user by sending textmessages or other forms of message to a personal device, e.g., asmartphone that is running a messaging application, and receivingresponsive messages from the user in return.

This specification uses the term “configured to” in connection withsystems, apparatus, and computer program components. For a system of oneor more computers to be configured to perform particular operations oractions means that the system has installed on it software, firmware,hardware, or a combination of them that in operation cause the system toperform the operations or actions. For one or more computer programs tobe configured to perform particular operations or actions means that theone or more programs include instructions that, when executed by dataprocessing apparatus, cause the apparatus to perform the operations oractions. For special-purpose logic circuitry to be configured to performparticular operations or actions means that the circuitry has electroniclogic that performs the operations or actions.

While this specification contains many specific embodiment details,these should not be construed as limitations on the scope of what isbeing claimed, which is defined by the claims themselves, but rather asdescriptions of features that may be specific to particular embodiments.Certain features that are described in this specification in the contextof separate embodiments can also be realized in combination in a singleembodiment. Conversely, various features that are described in thecontext of a single embodiments can also be realized in multipleembodiments separately or in any suitable subcombination. Moreover,although features may be described above as acting in certaincombinations and even initially be claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from thecombination, and the claim may be directed to a subcombination orvariation of a subcombination.

Similarly, while operations are depicted in the drawings and recited inthe claims in a particular order, this should not be understood asrequiring that such operations be performed in the particular ordershown or in sequential order, or that all illustrated operations beperformed, to achieve desirable results. In certain circumstances,multitasking and parallel processing may be advantageous. Moreover, theseparation of various system modules and components in the embodimentsdescribed above should not be understood as requiring such separation inall embodiments, and it should be understood that the described programcomponents and systems can generally be integrated together in a singlesoftware product or packaged into multiple software products.

Particular embodiments of the subject matter have been described. Otherembodiments are within the scope of the following claims. For example,the actions recited in the claims can be performed in a different orderand still achieve desirable results. As one example, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In some cases, multitasking and parallel processing may beadvantageous.

What is claimed is:
 1. A computer-implemented method for communicatingshared blockchain data, the method comprising: sending, by a consensusnode of a blockchain network, current state information associated witha current block of a blockchain to one or more shared storage nodes ofthe blockchain network, wherein the consensus node stores the currentstate information in a current state tree configured to include stateinformation that is updated or added due to transactions added to thecurrent block, wherein the one or more shared storage nodes storehistoric state information associated with every block of the blockchainas a historic state tree, wherein the historic state tree includeskey-value pairs (KVPs) with values being account states of accountsassociated with the blockchain network and keys being hash values of thecorresponding account states, and wherein the consensus node does notstore the historic state tree; sending, by the consensus node, a hashvalue to at least one of the one or more shared storage nodes forretrieving an account state stored in the historic state tree;receiving, by the consensus node, the account state in response tosending the hash value; and verifying, by the consensus node, that theaccount state is part of the blockchain based on the hash value.
 2. Thecomputer-implemented method of claim 1, wherein the blockchain networkincludes at least f+1 shared storage nodes and no more than 2f+2consensus nodes, and wherein f is a maximum number of faulty sharedstorage nodes and consensus nodes that can be tolerated within theblockchain network.
 3. The computer-implemented method of claim 1,wherein the one or more shared storage nodes are elected by receiving2f+1 votes from all 3f+1, 3f+2, or 3f+3 nodes of the blockchain network,and wherein f is a maximum number of faulty shared storage nodes andconsensus nodes that can be tolerated within the blockchain.
 4. Thecomputer-implemented method of claim 1, wherein the current state treeincludes KVPs with values being account sates associated with thecurrent block and keys being node IDs corresponding to nodes of thecurrent state tree and a block ID corresponding to the current block. 5.The computer-implemented method of claim 1, wherein the current stateinformation sent by the consensus node includes a digital signaturegenerated based on a private key associated with the consensus node. 6.The computer-implemented method of claim 1, wherein sending the currentstate information further comprises sending the current stateinformation and a hash value of the current state information as KVP tothe one or more shared storage nodes of the blockchain network.
 7. Thecomputer-implemented method of claim 1, wherein verifying that theaccount state is part of the blockchain is performed based on hashingthe account state to generate a hashed account state and comparing thehashed account state to the hash value.
 8. The computer-implementedmethod of claim 1, wherein the one or more shared storage nodes storehistoric state information locally or on a cloud storage.
 9. Thecomputer-implemented method of claim 1, wherein the current state treeand the historic state tree are stored as a fixed depth Merkle tree. 10.A non-transitory, computer-readable storage medium storing one or moreinstructions executable by a computer system to perform operations of aconsensus node for communicating shared blockchain data, the operationscomprising: sending, by a consensus node of a blockchain network,current state information associated with a current block of ablockchain to one or more shared storage nodes of the blockchainnetwork, wherein the consensus node stores the current state informationin a current state tree configured to include state information that isupdated or added due to transactions added to the current block, whereinthe one or more shared storage nodes store historic state informationassociated with every block of the blockchain as a historic state treewherein the historic state tree includes key-value pairs (KVPs) withvalues being account states of accounts associated with the blockchainnetwork and keys being hash values of the corresponding account states,and wherein the consensus node does not store the historic state tree;sending, by the consensus node, a hash value to at least one of the oneor more shared storage nodes for retrieving an account state stored inthe historic state tree; receiving, by the consensus node, the accountstate in response to sending the hash value; and verifying, by theconsensus node, that the account state is part of the blockchain basedon the hash value.
 11. The non-transitory, computer-readable storagemedium of claim 10, wherein the blockchain network includes at least f+1shared storage nodes and no more than 2f+2 consensus nodes, and whereinf is a maximum number of faulty shared storage nodes and consensus nodesthat can be tolerated within the blockchain network.
 12. Thenon-transitory, computer-readable storage medium of claim 10, whereinthe one or more shared storage nodes are elected by receiving 2f+1 votesfrom all 3f+1, 3f+2, or 3f+3 nodes of the blockchain network, andwherein f is a maximum number of faulty shared storage nodes andconsensus nodes that can be tolerated within the blockchain.
 13. Thenon-transitory, computer-readable storage medium of claim 10, whereinthe current state tree includes KVPs with values being account satesassociated with the current block and keys being node IDs correspondingto nodes of the current state tree and a block ID corresponding to thecurrent block.
 14. The non-transitory, computer-readable storage mediumof claim 10, wherein the current state information sent by the consensusnode includes a digital signature generated based on a private keyassociated with the consensus node.
 15. The non-transitory,computer-readable storage medium of claim 10, wherein sending thecurrent state information further comprises sending the current stateinformation and a hash value of the current state information as KVP tothe one or more shared storage nodes of the blockchain network.
 16. Thenon-transitory, computer-readable storage medium of claim 10, whereinverifying that the account state is part of the blockchain is performedbased on hashing the account state to generate a hashed account stateand comparing the hashed account state to the hash value.
 17. Thenon-transitory, computer-readable storage medium of claim 10, whereinthe one or more shared storage nodes store historic state informationlocally or on a cloud storage.
 18. The non-transitory, computer-readablestorage medium of claim 10, wherein the current state tree and thehistoric state tree are stored as a fixed depth Merkle tree.
 19. Acomputer-implemented system, comprising: one or more computers; and oneor more computer memory devices interoperably coupled with the one ormore computers and having tangible, non-transitory, machine-readablemedia storing one or more instructions that, when executed by the one ormore computers, perform one or more operations of a consensus node forcommunicating shared blockchain data, the operations comprising:sending, by a consensus node of a blockchain network, current stateinformation associated with a current block of a blockchain to one ormore shared storage nodes of the blockchain network, wherein theconsensus node stores the current state information in a current statetree configured to include state information that is updated or addeddue to transactions added to the current block, wherein the one or moreshared storage nodes store historic state information associated withevery block of the blockchain as a historic state tree, wherein thehistoric state tree includes key-value pairs (KVPs) with values beingaccount states of accounts associated with the blockchain network andkeys being hash values of the corresponding account states, and whereinthe consensus node does not store the historic state tree; sending, bythe consensus node, a hash value to at least one of the one or moreshared storage nodes for retrieving an account state stored in thehistoric state tree; receiving, by the consensus node, the account statein response to sending the hash value; and verifying, by the consensusnode, that the account state is part of the blockchain based on the hashvalue.
 20. The system of claim 19, wherein the blockchain networkincludes at least f+1 shared storage nodes and no more than 2f+2consensus nodes, and wherein f is a maximum number of faulty sharedstorage nodes and consensus nodes that can be tolerated within theblockchain network.